The Effect of Superposition on the Quantum Features of the Cavity Radiation of a Three-Level Laser

We study the statistical and squeezing properties of the cavity light produced by a degenerate three-level laser with the use of the solution of the pertinent quantum Langevin equation. Moreover, applying the density operator to the cavity radiation superposition, we investigated the quantum properties of the superposed cavity light beams generated by a pair of degenerate three-level lasers. Superposing the cavity radiation increases the mean and the variance of the photon number without affecting the quadrature squeezing. It is observed that the degree of squeezing of the separate cavity radiation, as well as the superposed cavity radiation, increases with the rate at which the atoms are injected into the cavity. We have also shown that the mean photon number of the superposed cavity radiation is the sum of the mean photon numbers of the individual cavity radiation. However, the variance of the photon number of the superposed cavity radiation turns out to be four times that of the component cavity radiation.

Interaction of Two-Level Atoms with a Single-Mode Quantized Radiation Field

We have studied the statistical and squeezing properties of the cavity light generated by a two-level laser. This optical system contains N two-level atoms available in a cavity coupled to a single-mode vacuum reservoir. They are pumped to the top level from the bottom level by means of the electron bombardment. Applying the steady-state solutions of the equations of evolution of the expectation values of the atomic operators and the quantum Langevin equation, we obtained the global and local photon statistics of the single-mode light beam. We have found that, for the two-level laser operating well above the threshold, the uncertainties in the plus and minus quadratures are equal and satisfy the minimum uncertainty relation. In view of this, we have identified the light generated by the laser operating well above threshold to be coherent. On the other hand, the light generated by the laser operating at threshold is found to be chaotic. From the obtained results, we have also observed that a large part of the local mean photon number, the local photon number variance, and the local quadrature variance are confined in a relatively narrow frequency interval.

Demise of Unruh radiation

Unruh radiation has attracted much interest, particularly because of its relationship to Hawking radiation. But its existence has been challenged by a variety of authors, including ourselves [Phys. Lett. A 158, 31 (1991)]. The absence of a consensus may be traced to the complex challenge of dealing with the infinite number of particles of the associated heat bath. Here, we show how this problem may be obviated by using the quantum Langevin equation [Ford et al., Phys. Rev. A 37, 4419 (1988); J. Math. Phys. 6, 504 (1965)], which enables us to present a simple argument to show that, despite the existence of an Unruh temperature, there is no Unruh radiation. A key point is that the Unruh system is an equilibrium system, in contrast to the Hawking system which is a non-equilibrium system.

Coherently Driven N Number of Degenerate Three-Level Atoms with Parametric Amplifier

We have analyzed the squeezing and statistical properties of the cavity light beam produced by a coherently driven degenerate three-level laser with a degenerate parametric amplifier (DPA) in an open cavity and coupled to a vacuum reservoir via a single-port mirror. We have carried out our analysis by putting the noise operators associated with the vacuum reservoir in normal order. Applying the solutions of the equations of evolution for the expectation values of the atomic operators and the quantum Langevin equation for the cavity mode operator, the mean photon number and the quadrature squeezing of the cavity light are calculated. And a large part of the mean photon number is confined in a relatively small frequency interval. Furthermore, we also obtain the antinormally ordered characteristic function defined in the Heisenberg picture. With the aid of the resulting characteristic function, we determine the Q function which is then used to calculate the photon number distribution.

Two-Level Atom with Squeezed Light from Optical Parametric Oscillators

The dynamics of a coherently driven two-level atom with parametric amplifier and coupled to a vacuum reservoir is analyzed. The combination of the master equation and the quantum Langevin equation is presented to study the quantum properties of light. By using these equations, we have determined the time evolution of the expectation values of the cavity mode and atomic operators. Moreover, with the aid of these results, the correlation properties of noise operators, and the large-time approximation scheme, we calculate the mean photon number, power spectrum, second-order correlation function, and quadrature variances for the cavity-mode light and fluorescence. It is found that the half-width of the power spectrum for the fluorescent light in the presence of a parametric amplifier increases, while it decreases for the cavity-mode light. Moreover, we have found the probability for the atom to be in the upper level in the presence of a parametric amplifier.

Quasi-Static Energy Transport between Nanoparticles

ABSTRACTWe consider energy transfer between non-equal nanoparticles mediated by a quantum system. The nanoparticles are considered as thermal reservoirs described as ensembles of finite numbers of harmonic oscillators within the Drude-Ullersma model having mode spacings Δ1 and Δ2. Our approach is based on the generalized quantum Langevin equation. The quasi-static energy transport between the thermal reservoirs is investigated. As is shown, the double degeneracy of the mode frequencies, which occurred in the previously considered case when Δ1 = Δ2, is removed in the present case of non-equal mode spacings. Equations describing long-time (t ∼1/Δ1,2) relaxation for the mode temperatures (or the ensemble averaged mode energies) are solved and the resulting expression for the total energy current between the nanoparticles is derived and explored.